Synchronous motor starting scheme



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Oct. 6, 1942. 1 A. KILGORE SYNCHRONOUS MOTOR STARTNG SCHEME Filed July27, 1940 2 Sheets-Sheet 2 QNxL xNvENToR Le@ /fy'are,

ATTORNEY WITNESSES:

Patented Get. 6, i942 steam srNcnsoNoUs Moron STARTING soeur/1e 1Lee A.Kilgore., Forest Hills, Pa., assigner to Westlnghouse Eiectrc &Manufacturing Company, Ea st Wittsburgh, Pa., a corporation ofPennsylt-anla Application `luly 27,

5 Claims.

vthe flexibility, efciencyend reliability of control,

particularly where a given load torque requirement might subject thesupply system to surges not permitted.

@ne broad object oi my invention is to combine armature control andfield control during the starting cycle of a synchronous inductionmotor.

.es more specliic object oi my invention is the provision of alternateeffective voltage control on the primary winding and control for the eldwinding oi a synchronous induction motor, which control for the armaturemay include variation of the eiective voltage by reactors, resistors,auto-` transiormers, or various arrangements of the connection ci thewindings or the armature, as changes from series star to series delta,or to parallel delta. or other combinations of these, and which controlfor the field winding may include ng the imedance ci the dischargecircuit o' one or more steps, or changing the poles, or both.

ects and advantages will become more om a study of the description as itd study of the accompanying drawnich:

gure l is a diagrammatic showing of my starting control system asapplied to a two-speed synchronous induction motor;

. Fig. 2 is diagrammatic showing of a modification oi my invention: and.

3 is a graphic showing of the novel results ined. with my controlsystems.

M designates generally the motor to d. The armature windings A com-'ality ci sections 3Q, til, d@ and @li and 'field windings F a pluralityof poles and or operation at two or more speeds. il have chosen thesimplest ytwo-speed motor merely to simplify the description but it isapparent to those skilled in the art that many more than iour poles maybe used and are usually used.

The controller C is shown as of the drum type operated at a constantspeed by a suitable constant speed motor (not shown). By operating thecontroller at constant speed all the starting steps are properly timed.I may, of courre, use electromagnetic control and inductive timing, or

1940, Serial No. 34?',904

field frequency type timing, to get the desired sequence of operationbut the discussion is probably simpler with the use of a drumcontroller.

The various contactcrs for effecting the steps in the starting cycle aredesignated.

i better understanding can probably be had from a study'oi a typicalstarting cycle. Assuming the buses i, ll and l5 are energized and theattendant operates the controller` to the iirst starting position, acircuit is thereby established from bus i, through conductors 2 and 3,contact fingers and G, bridged by controller segment E, conductor l,actuation coil t of the main line contactor and conductor i8 to bus il.

Gperation or" contacter 9 closes contact members i2, i3 and connectingbuses l, il and l5 so that the various armature circuits, to bepresently described, may be made.

Upon movement of the controller to the second position, a circuit isestablished from the energized segment 5 through contact finger i6,through closed contact members il, actuating coil i8 of contactor l@ toenergized conductor ES. A circuit is also established from segment Ethrough contact ringer lill, closed contact members 2f, actuating coil22 of contacter 23, to energized condoctor lll. fr further circuit isestablished from segment i through Contact nger 24, and actu-- atingcoil 2li oi contacter 26.

By operation of contactors i9, 23 and 2li, a series delta connection forthe armature windings A is established, and a low resistance dischargecircuit is established for the eld windings F.

The series delta circuit may be traced from junction 2l', throughContact members 2E and 29, windings and ill, Contact members 32,junction 33, Contact members 32 and 34, windings v35 and 3G, contactmembers 3l, junction 3S, contact members 3l and 39, windings il!! andfil, contact members 2B back to junction 2l.

The field windings on the other hand, though including a plurality ofpoles, are `connected, in effect, as two single-phase low-resistancecircuits. These circuits 'may be traced, for one, from slip ring 42through contact members 43, a relatively small portion of dischargeresistor 45, Contact members lll to slip ring B6, and, for the other,from slip ring 6l, contact members 48, a relatively small portion oresistor 49 and Contact members 5B to slip ring 5l.

This second starting step makes the field discharge resistance low. Thisis of advantage to protectJ the field winding against excessive voltage.This step may, however, not be necessary when the motor design andsupply voltage lected are such as not to produce excessive fieldvoltage.

The third step of the controller merely opens the circuit for coil 25 atcontact finger 24, thereby placing the entire resistors i5 and 43 in therespect'ive two discharge circuits of the field windings, and the fourthstep effects the reclosing of contact members 34 vand 60. Th torquevariations for these last three steps are illustrated by curve portions52, 53 and 5G shown in Fig. 3.

At the end of the fourth step, contact finger 55 is energized, thusestablishing a circuit for coil the eld.

After operation on the four poles as long as desired, contact ngers 61are energized and contact fingers |6 are deenergized. This effects thetransfer from series delta to parallel star connection. During thistransfer, contact finger 24 is, of course, also deenergized so as `tostart this induction motor cycle of operation on high resistance of theeld, since contact members 44 and 50 will thus be opened.

When contact finger 61 is energized, a circuit is established for coil68 of contactor 69 through contact members 69', and contact members 10to 15, inclusive, are closed. The parallel star circuit is thusestablished. This circuit may be traced from junction 21, throughcontact members 12, armature sections 35 and 36 in parallel to thejunction 16. The circuit from section 35 lto junction 16 is throughcontact members 34,

whereas the circuit for the right-hand end of 36 is through contactmembers 13 and 34.

For the armature sections 40 and 4|, the circuit is vfrom `junction 38through contact members 10 and then sections 40 and 4| in parallel tojunction 1B. The circuit for section 40 may be completed through contactmembers 39, 13 and 34 to junction 16,'whereas the circuit for section 4|is completed through contact members 29, 15 to junction 16.

For the armature sections 30 and 3|, the circuit is from junction 33through contact members 14 and then Asections 30 and 3| in parallel tojunction 16. The circuit for section 30 is comple`ted through contactmembers 15 to junction 16, whereas the circuit for section 3| is directto junction 16.

In the eighth controller position, nger 24 is again energized. Thismeans that the field discharge resistance is changed from highresistance to low resistance. f

In the ninth position, finger 55 is again energized. This means thefield is again energized with direct current, but in this positioncontact finger 11 is also energized. A circuit is thus established forcoil 18 of contactor 19. This contactor connects the field for two poleor high speed operation. l 'I'he two-pole circuit may be traced fromenergized conductor 58 through contact members 60.

l windings 6l and 62, contact members 80, resistor 8|, windings65 and64, contact members 82 and` 66 to energized conductor 5l.

Note that the connections for windings or poles 65 and 64 are reversed,thus making poles 6| and 65 alike and poles 62 and 64-alike.

After the motor has synchronized, namely, is at 100% speed, the field isagain removed and before the motor has a chance to drop in speed anyconsiderable extent the 'armature is transferred from parallel star toparallel delta. It is a distinct advantage to make this transfer fromsynchronous speed to, say, 95% speed than from 95% speed to 90% speedif' this transfer were attempted from parallel star to parallel deltawithout the two-pole synchronization.

The parallel delta armature connection is effected at the eleventhcontroller step, when finger 03 is energized. In this position coil 84of contactor is energized through closed contact members 85', andcontact members 86, 81 and 88 are closed. The parallel delta circuit isthus established.

This circuit may be traced from junction 21 through contact members 12,thence through Winding 35, contact members 13 and 31 to junction 38 anda parallelcircuit through winding 36 and contact members 31 to junction38. A second side of the delta connection is from junction 38, contactmembers 10, winding 40, contact members 1| 88 and 14 to junction 33 andaparallel circuit through winding 4| and contact members 88 and 14 tojunction 33. The third side of the delta connection is from junction 33through contact members 14, winding 30, contact members 15, 81 and 12 tojunction 21 and a parallel circuit throughv Winding 3| and Contactmembers 81 and 12 to junction 21.

The motor thus operates on parallel delta first with high fielddischarge resistance and then on low-resistance since contact finger 24is energized in the twelfth controller position.

In the thirteenth position, finger 55 is energized and as a consequencethe motor is synchronized on two poles or high speed operation.

In Fig. 3, curves 52, 53, 54, etc., illustrate the various torquevariations and also illustrate how vthe toque curves can be made toclosely follow the load torque curve without causing excessive surges.

The modification shown in Fig. 2 illustrates a system in which the`effective voltage of the primary winding of a synchronous motor isvaried by means of reactors and a plurality of values of resistance areutilized in the eld circuit of the synchronous motor to obtain thedesired torque characteristic.

Assuming that the buses |0|, ||0 and ||4 are energized from a source ofpower (not shown) and that the controller C is operated to the rststarting position, a, circuit is thereby established from bus |0|,through conductor |02, contact fingers |04 and |06, bridged bycontroller segment |05, actuation coil |01 of the main line contactor|08 and conductor |08 to bus H0.

Operation of contactor I 0 9 closes contact mem- |22 and conductor |09to bus |I.0. Operation of contactor |22 closes contact members |23,

A further circuit is established in the first position ot controller C'from the energized contact finger we through controller segment $95,contact finger 121i, actuation coil 12a oi contacteri2l, and conductorlili to bus iii). Operation of contacter 12% closes contact membersi128.

Byioperation of contactors liland i2?, the field winding |28 of motor Mis connected through a relatively small portion o resistor l to therebykeep the iield voltage to a minimum. lt will readily be understood thatresistor i3@ may ce a field discharge resistor or a starting resistor.

After the controller C has eeen advanced through a plurality ofpositions, for example, two, to allow suilicicnt time for the motor toreach es high a speed as can ce attained with this set ci connections,the controller C' is 'then advanced to the third position. In the thirdposition oi the controller, segment Miti disengages contact finger it!to open the circuit through coil it oi contacter il, thus causingcontact members H3 shooting a portion ci resistor i3@ to open to therebyinsert suiiicient resistance .in the circuit of iield 'winding HS togive high torque at this speed. lt will readily ce understood that ioyuti lising a plurality oi contactera itl, selectable portions ofresistor 12d :nay he inserted in the field circuit at will.

After the motor accelerates further, the controller C' is advanced tothe fourth position when controller segment ille completes the circuitfor energized contact linger lili through con-I tact finger iii,operating coil i332 oi contacter i133 and conductor litt to ilusOperation oi contacter E33 closes contact members lt, i355 and ill?,thereby shouting the reactorrJ ii, H and ii, respectively, andcorinectincr the primary windings iid to the buses lill, iii? and iii.

After allowing the motor to accelerate to c. higher speed, controller C'is advanced to position E when contact finger 124 is again energized.thus reclosing the circuit of iield winding im through contact membersH8 to give a. low resistance suitable to give maximum torque at lowslip.

In the sixth position of controller C, segment H bridges contact fingerslili and ill to complete the circuit for energizing operating coil In oicontacter 139. Operation oi contacter i causes contact members No and llto close, thereby energizing field 29 with direct current from thesources 142 and M3, causing,T the motor to pull into step and operate atsynchronous speed.

Also in the sixth position of controller C, segment 105 disengagescontact fingers H9 and 124, thereby deenergizing operating coils Hl andHS, thus opening the circuit through resistor 130.

It 'will readily be understood that the reactors H8, Hl and H8 may beshunted in more than one step by utilizing additional contactors 33 eachshunting a portion ci the reactors. Furthermore, it will be understoodthat reactors H8, H7 and H8 and contacter 133 may be omitted and theprimary winding H5 may then be connected to the buses Mi, lll) and H4directly through contact members HI, H2 and H3. The sequence ofoperation will be the same as hereinabove described in connection withFig. 2, eX- cept'l that the step corresponding to the fourth position oncontroller C' is omitted.

Another variation may be arranged by utilizing an auto-transformer toobtain reduced voltage on the primary windings il! in a manner wellknown to those skilled in the art. It will be understood that thesequence of operation may be the same as that hereinabove described inconnection with Fig. 2.

I am, of course, aware that others, particularly after having had thebenefit of my teachings may device other circuit diagrams foraccomplishing the same or similar novel results. i, therefore, do notwish to "oe limited to the particular syste'n or" control shown anddescribed, but Wish to he limited only by the scope oi the claims heretoappended.

'i claim as my invention:

i. in a system of control ior a synchronous induction motor, incombination; o twospeed synchronous induction motor having amaturewindings comer-icing c, plurality of sections that may he connected inseries delta, parallel star and parallel delta, and .Field windingscomprising a plurality of pole windings that may connected for twospeech; a source of alternating current; a source oi' direct current;discharge resistors for the Field windings; means `lor simultaneouslyconnecting the armature windings in series delta, and connectingportions o the discharge resistor to the iii-.eid windings; means forvarying the resistance ei'rect of the iieid discharge resistor; meansfor connecting the field winding for los! speed operation to the sourceci direct current; means for transferring the arman ture Winding fromseries delta to parallel star; and 'transferring the field to fielddischarge connection; means for varying the :field discharge resistorresistance 'while the paralisi stai connection maintained; means 'forconnecting the 'iield i'or high speed operation; means fortragisierrins; the high .speed field connection to charge circuitconnection; and nies-im operable immediately aiter the last named meansfor transferring the armature connection porallei star to paralleldelta; means t r varying the resistance value of the :del dischargeresistor nalhilc the parallel delta armature connection is maintained;and means for opening the field discharge circuit and simultaneouslyenergizing the 'Zieid for high @eed operation.

2. in e. system of control for a synchronous induction motor, incombination, a synchronous induction motor having armature windings andheld windings, and field discharge circuits, said held dischargecircuits being designed to materially alter the starting torquecharacteristics during starting, if the resistance characteristics oithe discharge circuits are varied: a source of alternating current, asource of direct current; means for connecting the amature winding tothe source of alternating current, held excitation control means forconnecting the field to the source of direct current; means for varyingthe effective voltage of the source of alternating current on thearmature in a plurality of successive steps, means for varying theresistance characteristic of the eld discharge circuits oy a pluralityofsuccessive steps during each step .of effective voltage variation, andmeans for causing operation of the' field excitation control means totemporarily excite the held windings with direct current at the end of aset oi steps varying the resistance characteristic of the fielddischarge circuits before the next step for varying the efiectivevoltage of the source of alterhating current is taken.

3. In a system of control for a synchronous induction motor, incombination, a two-speed synchronous induction motor having amaturewindings and neld windings wound for several speeds and field dischargecircuits, said field diqcharge circuits being designed to materiallyalter the starting torque characteristics during starting, kif theresistance characteristics of the discharge circuits are varied; asource of alternating current, a source of direct current; means forconnecting lthe armature winding to the source of alternating current;leld excitation control means for connecting the iieid to the source ofdirect current for one speed of operation; means for varying theeffective voltage of the source of alternating current on the armaturein successive steps, and means for varying the resistance characteristic.of the ileld discharge circuits during each step of effective voltagevariation, and means for causing operation of the eld excitation controlmeans after a given variation of the resistance characteristic of theiield discharge circuit to effect a dii'erent speed of operation.

hln a system of control for a synchronous induction motor, incombination, a synchronous induction motor having amature windings andfield windings, and field discharge circuits, said eld dischargecircuits being designed to materially alter the starting torquecharacteristics.

during startinglf the resistance characteristics of the dischargecircuits are varied; asource of alternating current; a source of directcurrent; means for connecting the armature winding to the source ofalternating current, iield excitation control means for connecting theeld to the source of direct current; means for varying the effectivevoltage of the source of alternating current on the amature in ayplurality of successive steps, means controlling the ileld excitationcontrol lmeans for temporarily eiecting' energization of the field withdirect current after certain steps other than the last step changing theeective voltage of the source of alternating current, and meansio'rcontinuously exciting the iield windings after the last step changingthe effective voltage of the source of alternating current.

5. In a system of control for a synchronous induction motor, incombination, a two-speed;

synchronous induction motor having armature windings and field windingsWound for several speeds and eld discharge circuits, said fielddischarge circuits being designed to materially alter the startingtorque characteristics during starting, if the resistancecharacteristics of the discharge circuits are varied; a source ofalternating current, a source of direct current; means for connectingthe armature winding to the source of alte. nating current; iielclexcitation control means for connecting the 'leld to the source ofdirect current for one speed of operation; means for varying the eectivevoltage of the source of alternating current on the armature insuccessive steps, means controlling the field excitation control meansfor eecting, energization of the field with direct current after eacheiective voltage step, said last named means including means forchanging the number of iield poles after certain steps changing theeiective voltage.

l LEE A. KILGORE.

